In airports, aircrafts are often towed by tractors, more particularly in the vicinity of air terminals. For this purpose, it is known to connect an aircraft to a tractor using a bar fastened to a fastening point located on the auxiliary landing gear of the aircraft, more precisely on the lower part of the latter which carries the wheel or wheels. Towing the aircraft using a tractor especially adapted for towing the aircraft directly by the wheels, of the auxiliary landing gear is also known. To enable the lower part of the landing gear to be steered to follow the motions imposed by the tractor, it is important to uncouple such lower part from the rest of the aircraft in rotation.
Such uncoupling can be obtained by uncoupling the arms of the torque linkage which connect the lower part to the wheel steering element, the function of which consists in steering the wheel or wheels in response to a steering command given by the pilot. Such method has the disadvantage of requiring the intervention of a ground operator as close to the auxiliary landing gear as possible, which can be dangerous if the pilot unduly activates the steering element. Besides, it is sometimes difficult to connect the arms of the torque linkage to each other, when the towing is completed. In addition, the ground operator can forget to connect the torque linkage arms upon completion of the towing.
Such uncoupling can also be obtained by deactivating the steering control, i.e. by placing the steering control in a free steering mode, in which the steering element becomes passive and leaves the rotation of the lower part of the landing gear free, which avoids separating the arms of the torque linkage. In this last case, the auxiliary landing gear is generally equipped with a neutralization lever which is activated by a ground operator to place the steering control in a free steering mode. Then again, the operator must get as close to the auxiliary landing gear as possible to activate the neutralization lever Besides, a lever is carried by a neutralization element positioned on the auxiliary landing gear, in an uncovered area exposed to bad weather and to vibrations, which may lead to a malfunction of the lever or of the associated contactor. Then, the towing may be performed when the steering control has not been placed in the free steering mode, such that the non neutralized steering control attempts to oppose any steering of the wheel caused by the tractor towing the aircraft to keep the wheels in the orientation requested by the steering control, which can lead to a deterioration of the towing bar and of its hook on the auxiliary landing gear, and in any case to a useless fatigue of the steering element. Besides, the operator can simply forget to activate the neutralization element, which can result in the same disadvantages.
To remedy these disadvantages, it was thought to position the neutralization lever under cover, i.e. directly in the aircraft cockpit. Thus, the pilot himself activates the neutralization lever to place the steering element in free steering mode with a view to enable the towing of the aircraft. But the pilot can also forget to activate the neutralization lever which can result; in the same disadvantages. Besides, when the pilot is not in the aircraft, a second operator must take the controls to activate the lever, which is not practical.